SOLUTION: Can you please help me on this word problem...the profit on a watch is given by p=x^2-13x-80, where x is the number of watches sold per day. how many watches were sold on a day wh

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Question 73113: Can you please help me on this word problem...the profit on a watch is given by p=x^2-13x-80, where x is the number of watches sold per day. how many watches were sold on a day when there was a $50 loss.
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
The profit is:
p+=+x%5E2-13x-80
Find x when p = ($50.00) The parentheses indicate a loss so this really should be written as -$50.00.
So, you want to substitute p = -50 into the formula and solve for x, the number of watches.
-50+=+x%5E2-13x-80 Add 50 to both sides and write the quadratic equation in standard form.
x%5E2-13x-30+=+0 This can be factored.
%28x%2B2%29%28x-15%29+=+0 Apply the zero product principle.
x%2B2+=+0 and/or x-15+=+0
x+=+-2 Discard this solution as one cannot make a negative number of watches.
x+=+15 This is the solution.
15 watches were made on the day when there was a $50.00 loss.